Research On Assembly Gap Compensation For Aircraft Composite Components

Because of high specific stiffness, specific strength, fatigue resistance, corrosion resistance and other excellent performance,composite materials are more and more widely used in aircraft structures. On the other hand, composite component manufacturing precision is not easy to control, and composite materials are high in rigidity, brittle in matrix, and weak in interlaminar strength. If there is gap between composite parts and no shimming is applied, larger assembly stress will be generated. Compulsory assembly will easily lead to damage in its internal structure. Research on aircraft composite gap compensation, and the influence of shimming on the interstitial strain and stress, has important theoretical significance and engineering application value.The primary contents of the thesis are as follows:For typical aircraft composite structures, such as spars, ribs, and panels, assembly is analyzed. Based on the practical measured errors of dimensions and shapes, the shape, magnitude and distribution of the gaps between composite parts during assembly are analyzed, and the geometrical model for the gap of composite assembly is built.Aiming at the built geometrical model of composite component assembly, in consideration of mechanical connection, without and with compensation(shimming) composite components are analyzed. The relations between shimming stiffness and stress and strain of composite components are qualitatively analyzed. A finite element model is built And the influences of shimming methods and parameters on strain and stress of composite parts are studied. A damage analysis program is designed on ABAQUS and the progressive damage analysis on composite components are carried out.Experiments of composite component assembly gap compensation are designed. The experiment device is developed, and the test liquid shims and solid shims are prepared. High lock bolt pre-tightening force load is exerted on the specimen, and then specimen strain is measured. Through the composite material constitutive equation the specimen stress is calculated. The experiment data is analysed, and through a comparison between the results of experiments and finite element analysis, the theoretical analysis results are verified.